Help me choose motor/esc for this boat

[tlandauer]

You are welcome!
Can't wait to hear from you how she runs, best of luck!

Sent from my Droid using Tapatalk 2

[corsara]

Damnit, I can't stop posting in this thread... Ok, now that I've ordered the ESC as well, I'll sum it all up here for future reference and in case somebody else ever buys the same hull, and wonders if somebody already did something with it.

Here are all the parts I bought for this boat:

Hull with hardware: http://www.r2hobbies.com/rc-boats/ar...cing-boat.html
Motor: http://www.offshoreelectrics.com/pro...o-2860&cat=148 (the 3400kV version)
Cooling jacket: http://www.offshoreelectrics.com/pro...eo-2840-jacket
ESC: http://www.offshoreelectrics.com/pro...er-seaking-120 (out of stock, bought elsewhere)
Servo: http://www.offshoreelectrics.com/pro...p?prod=dh-2075 (I just realized it's too big, so I'll find a Traxxas 2060 or 2065, which will fit the hole precisely without modifications).
Servo arms: http://www.offshoreelectrics.com/pro...hp?prod=dh-670
Universal joint: http://www.offshoreelectrics.com/pro...prod=grp-354.4 (out of stock, bought elsewhere)
Props: 34.5, 37.5, 39 and 40.5. Also one triple blade 36mm. All carbon filled for testing.
Tabs: http://www.offshoreelectrics.com/pro...od=ose-tab1015

After I get all parts and put it all together, I'll be testing and having my older daughter take videos, which I'll post here to show all of you how it turned out :) I guess this boat will be too big for my 18x36 pool, so closest big water is lake Ontario, although I've seen smaller lakes around near parks.

Once this is done, I intend to get my hands dirty with even more exciting stuff, such as building this 30" cat from scratch like this guy did: http://www.rcgroups.com/forums/showthread.php?t=1157639

For that I'll definitely need the bigger 36xx motor I think :)

Cheers!

[Spartanator]

??
Thanks for the heads up though, another ESC bites the dust!

I know, but I hear they are .......... Not going to mention much yet as I don't want to start 1000 rumors. Don't worry, bumped a few emails back and forth and I know they are working. Just wanted to give any guys a heads up so they don't waste effort on future builds...

[corsara]

My parts from OSE arrived in record time, I'm amazed! I'll definitely be a customer in the future! Still waiting on the ESC that I ordered from a different place.

In preparation for all of this, I have a few questions if somebody can help with:

1) For cooling, which sequence is better:
a) inlet => ESC => motor => outlet
b) inlet => motor => ESC => outlet

2) The official specs for the motor are:
-- max amps: 80A
-- Lipo Cell: 17V
-- Max Power = 1300W

I want to go with a 3S 5000mah battery. Am I right to assume that if it is 25C rated, then I can have max of 5 x 25 = 125 Amp draw from it? Similarly, if it's 30C, I can have max of 5 x 30 = 150 Amp draw?

Further more, since 3S is 11.1V, then 1300W / 11.1V = 117 Amp max from motor, which is OK with both a 25C and 30C battery?

Or 80A x 11.1V = 888W - max power of this motor on a 3S battery?

Just trying to see if I'm calculating stuff correctly.

Thanks.

[kfxguy]

Cool esc first then motor is what most people do on here. ive done it both ways only because of component layout. Didnt see any difference in my experience but it is best to cool the esc first as its more sensitive to heat than the motor.

[Fella1340]

It's a good thing the motor mount isn't perpendicular to the drive shaft/stuffing tube. You need to run the universal at an angle to keep the shaft loaded in the stuffing tube or everything would be banging around. That's what I picture happening if everything was in a straight line and the stuffing tube has clearance around the shaft. The aq motor and esc mentioned earlier puts my 29" revolt up to almost 50mph, it would be ideal for your setup. I have to get one to put in 24" I have. 28mm motor seems small to me. Good luck

[corsara]

Cool esc first then motor is what most people do on here. ive done it both ways only because of component layout. Didnt see any difference in my experience but it is best to cool the esc first as its more sensitive to heat than the motor.

Thanks.

It's a good thing the motor mount isn't perpendicular to the drive shaft/stuffing tube. You need to run the universal at an angle to keep the shaft loaded in the stuffing tube or everything would be banging around. That's what I picture happening if everything was in a straight line and the stuffing tube has clearance around the shaft. The aq motor and esc mentioned earlier puts my 29" revolt up to almost 50mph, it would be ideal for your setup. I have to get one to put in 24" I have. 28mm motor seems small to me. Good luck

Yeah, I ordered the correct size u-joint. As for the motor---I already bought it as I wasn't sure if I'll fit a 36xx motor in the space. We'll see how it goes.

[Fella1340]

I just went and looked at my r2hobbies hull, Its the same boat you have without the flood chamber. The original motor I had in it was a 28mm x60 long 2 pole, it had the cooling jacket built into the motor. It was a really cheap motor (junk really)and I ran it on 4s until the esc and motor died. Moved very well for using poor quality stuff in it. The hull was definitely good for a lot more speed and it handled very well, turned on a dime once I added turn fins.
Would you mind posting some pictures of the inside of the boat showing the flood chamber whenever you get the chance please. I should have bought the self righting version originally and I have it apart for a refit so nows a good chance. It's the hull I used to learn on as well including doing a carbon fiber inlay on. You should be pleasantly surprised with it, it's a boat I will be keeping because it's a lot of fun to drive. Your should really fly with the motor your putting in it!

[corsara]

Not sure what you meant by "inside of the boat showing the flood chamber", but here are some pics I made for you.

BTW, the motor is there just for test-fit---I didn't have a good length screws, hence the washers. I'll pick up shorter screws tomorrow. Can't wait for the other parts to arrive to finish this toy :)

[corsara]

I'll be stopping by the local hobby shop tomorrow, and it's a good time to buy the battery.

Just measured and I see I've got lots of space to fit whatever I want, so I can't make my mind between a 3S or 4S (or 2 x 2S) battery. Obviously my motor can handle the 4S as specs list it as maximum 17V, and maximum 80A draw. ESC can handle that too (120A).

If I go with 3S, I have the option of 5000, 6400 or 8000mAh, which will fit with plenty of space to spare as well.

I don't know what to do. My transmitter has a dual-rate adjustment, so it's easy to dial down the output and still have a complete trigger travel for the throttle if things are too much out of hand with the 4S. Any thoughts?

EDIT: I read again some of tlandauer's points earlier in this thread, and after doing some calculations---I think I'm almost set at buying a 3S battery. At full charge, the motor will be capable of producing more than 35,000 rpm, which seems plenty, even over the top.

[tlandauer]

I am @ work, just a headsup, dual rate is for steering, you should not drive the boat less than full throttle, part throttle will be very bad for your ESC, I got to go, but remember this.

Sent from my Droid using Tapatalk 2

[corsara]

I am @ work, just a headsup, dual rate is for steering, you should not drive the boat less than full throttle, part throttle will be very bad for your ESC, I got to go, but remember this.

Sent from my Droid using Tapatalk 2

Hi. Yes, prompted by your reply, I read in some other threads why running at partial throttle is a bad idea. I'd like to think that getting a bigger ESC than I actually need for this setup (120 amps vs 60 amp I could get away with) will alleviate this problem a little. Also, the Seaking has overheat protection. Either way, I'll get the 3S battery and see how it goes. Thank you.

[corsara]

Small update: bought a Duratrax 3S 11.1v 6400mAh 25C battery today. If only my other parts were in already (ESC, servo, u-joint)...

Thinking about installing the trim tabs. I already know they should be about 1mm above the bottom. Anyone knows how close to the keel they should be? In my case---the closer they are, the easier the install will be.

Also, any tips on how to water-seal the holes I'll make for the screws that hold the tabs?

Update: I also asked some questions regarding the trim tabs in another thread: http://forums.offshoreelectrics.com/...s-installation

[tlandauer]

" Also, any tips on how to water-seal the holes I'll make for the screws that hold the tabs? "

I use silicone sealant, but plumber's putty is highly recommended. Problem with the silicone is that if that is used and later one wants to paint the hull, paint will have a hard time sticking to the surface properly. Also if you get too much inside ( messy job) , should you want to glue something, it will be impossible. Silicone is like oil and next to impossible to wash off, even with chemicals.
That said, I never had to deal with these issues because my hull is either painted already or doesn't need painting and the inside set up usually is already done correctly. I put a thin layer on the mounting surface and also dab a bit on the screws, that's all. Any bathroom silicone sealant that is sold at hardware store will do.

[corsara]

Alright guys, tonight I finished the boat (almost). I will be making a very short slow speed test run tomorrow in my swimming pool. However, I'm still waiting on two parts, and only when I get them I'll go to the lake (I bought an inflatable boat for 2 to have at hand in case of an accident). I'm missing these things:

- A proper 4mm to 4mm universal joint. For my test run tomorrow, I drilled the u-joint that came with the hull--it was 3.2mm to 4mm. I didn't do a perfect job, it is ever so slightly off-center, even though I used my hand press (no access to lathe).

- The 11.1V 6400mAh battery still hasn't arrived (it was a special order at the LHS). I'll conduct my test with a 7.4V 2000mAh Lipo that I have from another thing. I wonder if that's going to be a mistake!

Below are some photos, I think it turned out alright for a first boat. The only thing I'm not sure about is the way I've held down the ESC---I used two cable ties, and I wonder if I should put something to dampen the vibrations. Also, I put the receiver in a balloon to keep away any potential water. I'll use hockey tape to hold down the hatch, and the only place that is not water-tight is where the water tubing goes into the boat (maybe I should put some silicone?!).

Here are the pics: